The present invention relates to an optical component comprising an optical waveguide structured in a core layer and to a photonic device comprising at least one such optical component.
Optical components comprising an optical waveguide are part of planar photonic devices. Such optical components can be designed to function, among other things, as multiplexers, switches or filters. The optical waveguides within such an optical component are used for carrying light e.g. from one part to another one of the planar photonic devices. In the past, the number of optical components formed within a photonic device has been increased continuously. Such an increase of optical components integrated in a single photonic device implies a higher compactness and/or the ever increase of optical signals to be transmitted through the same optical waveguide leading to stringent working conditions. This is particularly the case concerning the tolerable stray light possibly present at some parts of the photonic device. Indeed, such stray light can be the origin of cross-talk and optical noise. Hence, the-presence of stray light may directly deteriorate the overall performance of the device. Therefore, there is a real need to alleviate or eliminate stray light.
WO 01/33263 A1 discloses a method of filtering optical noise generated by an optical component in a planar photonic device. The planar photonic device in which this method is implemented comprises refractive index change regions. These regions are placed symmetrically on either side of the path of the light downstream from the optical component and are adapted to prevent forward propagation of the light outside said path. The refractive index change regions can be constituted by trenches or by regions possessing saw tooth-shaped elements etched in the photonic devices. This prior art document explicitly teaches to use refractive index change regions in a symmetrical configuration, that is on both sides of for example an optical waveguide carrying the light. The design of the planar photonic device is strongly restricted due to the necessity of a symmetrical configuration of the refractive index change regions. Beside that, the necessity of a supplementary etching process is inevitably associated with a higher manufacturing cost factor of such photonic device.
In U.S. Pat. No. 6,298,178 B1 is described an alternative by doping selected areas of the substrate on which an integrated optical circuit is formed. Those selected areas show accordingly the property of absorbing light. When designed in an appropriate way in the vicinity of the integrated optical circuit, these selected areas will absorb stray light present in the substrate which is not guided by components of the optical circuit. Despite a different approach compared to WO 01/33263 A1, it has clearly the same disadvantage as quoted above.
U.S. Pat. No. 6,212,307 B1 [EP806685] discloses an integrated optical device which has an optical microguide of index n0 between two confinement layers of index respectively n1 and n1′. The index n0 of the microguide exceeds both indices n1 and n1′ such that any radiation introduced into said microguide propagates along the axis of the latter. Filtering means constituted by at least one reflector element are placed on at least one side of the microguide, the reflector element having at least one element etched in layers of index n1 and/or n1′ and/or n0. In this approach, the problem of stray light is overcome by reflector elements which reflect the stray light away from the microguide. Besides showing similar disadvantage as the two previous examples, the reflecting elements must be designed in a relatively large scale to obtain a satisfying effectiveness. This restricts substantially its application.